Photoacoustic correlation spectroscopy for calibration-free absolute quantification of particle concentration

Currently, laser fluence calibration is typically required for quantitative measurement of particle concentration in photoacoustic microscopy. In this paper, we present another quantitative approach to measure absolute absorber concentrations by photoacoustic correlation spectroscopy. The proposed method is based on the fact that the Brownian motion induces particle count fluctuation in the detection volume. We first derived a theoretical model for photoacoustic signals and then applied our method to quantitative measurement of different concentrations of various particles. The experimental results agreed well with the predictions from the theoretical model, suggesting that our method can be used for absolute particle concentrations measurement.